Treatment of mechanical fabrics



Patented May as, i942 V ETEE TREATMENT OF MECHANICAL FABRICS Carlton G.Gordon, Elsmere, N. Y., assignor to Albany Felt Company, Albany, N. Y.,a corporation of New York N Drawing. Application December I, 1939,Serial N0. 307,114

6 Claims. (Cl. 8-428) My invention relates solely to the treatment ofwool, and to the treatment of mechanical fabrics which are made in wholeor insubstantial part of wool, whereby their resistance to stretchingand disintegration under attack by alkaliesf and alkaline solutions suchas those of caustic soda, silicates, phosphates, carbonates or lime,andcertain bleaches such as chlorine, hypochlorous acid andhydrosulphites is greatly enhanced and the life of the fabrics therebysubstantially prolonged. By the term, mechanical fabrics," I mean toinclude fabrics 'such as paper machine felts and jackets, slasher clothand jackets,

for such purposes as wearing apparel, floor coverings, bed blankets,unholstering and the like.

My process is not limited in its application to wool after the same hasbeen reduced to the form of a fabric but may beapplied to raw wool,loose roping, yarn and the like, although the advantages of thetreatment will probably not be rec ognized until the wool is in thefabric form. Furthermore, the treatment is not limited to mechanicalfabrics consisting entirely of wool but may be used in the treatment ofsuch fabrics having a substantial portion of wool therein but alsocontaining some vegetable fibers, such for example as a cotton or linenwarp.

table fibers in the fabric but the resistance of the wool portion to thedestructive effect of any of the media mentioned above is so greatlyenhanced as entirely to offset any detrimental effects on the otherfibers. V

Broadly, the process consists in impregnating It cannot be said that thetreatment improves the vegethe wool with a chromium compound, and this,

in general, is accomplished intwo steps. First, the wool or wool fabricis chromed by treating it in an acid solution of an alkali chromate ordichromate, or chromium trioxide, and fora long enough time to develop adark brown color. For

example, I may use chromium trioxide, or a chromate or dichromate ofammonium, potassium, sodium, lithium, calcium, strontium, or

barium; sodium dichromate being preferred be-.

cause there is more active ingredient present therein than in thechromate, and because of its cheapness and ready solubility. This mayrequire from 1 to 6 hours depending upon the temperature and theconcentration used. Thereafter,

an-acid, sulphur dioxide, or hydrosulphite are suitable reducing agents.This step may require from a few minutes to several hours depending uponwhich reducer is used, the concentration thereof and the temperature atwhich the process is conducted. This step is followedby a good rinse.

The general range of the chromium compound used may be between about 5lbs. and about 25 'lbs. per 100 lbs. of wool treated. The temperature atwhich my process is conducted may vary from normal room temperatures(about F.)

up to the boiling point of the solution, but since heat, in and ofitself, may substantially deleteriously affect the strength andsoundness of a wool fabric, the process is preferably conducted withinthe temperature range'of about F. to 120 F. v

As stated above, the intermediate rinse between the two treatment stepsmay be eliminated and the second step conducted by incorporating thereducing agent in the bath used for the first step; it being understoodthat, in any case, although a single. bath may be used the process isnevertheless conducted in two separate steps. However, this procedureresults in a, considerable loss of time and chemicals.

As a specific example let it be assumed, that a papermakers feltweighing from about 70 lbs. to lbs. is to be treated. The feltis put ina tub, in which preferably a circulation of the liquid contents can bemaintained, or which is equipped with some means for providing relativemovement of the felt and liquid to insure uniformity of treatment,together with about 100 gals. of water and'heated to F. Three lbs. ofmuriatic acid diluted with water are then added and followed by theaddition of 15 lbs. of sodium dichromate previously dissolved in water.The dichromate solution is added in small quantities over a period ofabout ten minutes. Six lbs. of muriatic acid diluted with water are thenadded slowly. The temperature of the solution is preferably maintainedat about 110 F. and the felt is treated therein for from 2 H13 hours.The solution is then dropped and the felt rinsed with clear waterseveraltimes; the last rinse being heated to 110 F. and left in the tub. Ten.lbs. of sodium thiosulphate and 6 lbs. of muriatic acid are added to'thebath. The thiosulphate is first dissolved in water and the acid isdiluted before being added, and the addition should be done over aperiod of about ten minutes. The felt is treated in this solution forabout 30 minutes whereupon; the solution is dropped andthe felt rinsedwith clear water. One hundred gals. of water at 110 F. are then run intothe. tub. vFive lbs. of sodium thiosulphat dissolved in water are addedand followed by the addition of 3 lbs. of muriatic acid diluted withwater. The felt is treated in this solution for ten minutes whereuponadditions of 5 lbs. of sodium thiosulphate and 3 lbs. of muriatic acid,as described above, are made several times so that the solution ismaintained a milky green color; it being understood that the temperatureof the bath is preferably maintained at about 110 F.

Sometimes a total of 40 to 45 lbs, of the sodium thiosulphate may berequired and usually 1 to 3 hours from the time the first thiosulphateis added are necessary to complete this step.

When the reduction has been completed the felt is thoroughly rinsed andtaken to the finishing room for other processes. After a felt has beengiven my treatment it is made substantially more resistant to certainchemicals but less resistant to others. In other words, the desirabilityof the treatment will depend upon the conditions under which the felt isto be used.

In order to show the resistance to a lime solution of a felt treated bymy process, strips thereof which, before treatment, normally had a Wetbreaking strength of 98 lbs. and a stretch of 16 1 72, under a 30 lb.load were subjected to a saturated lime solution for 6 hours atapproximatel 120 F. This treatment reduced thev breaking strength to 54lbs. and the stretch was increased to 21% under a 30 1b. load. Duplicatestrips from the same felt which had been given my treatment were treatedin the same lime bath for the same length of time and upon removalshowed a breaking strength of 64 lbs. and a stretch of only /2% under a30 1b. load.

From the foregoing it may be seen that my treatment allowed the feltstrips to retain more of their original strength after the injuriouslime bath and the stretch was very substantially less than that of theuntreated strips. Both of these properties obviously indicate a sounderfelt.

- New felt strips having a normal wet breakin strength of 95 /2 lbs. anda stretch of 15 under a load of 30 lbs. were subjected to a 30%hydrosulphite solution (based on the weight of the wool) for 5 hours at160 F. After the treatment the felt strips which had not been treated bymy process had a breaking strength of 57 lbs, and a stretch of 36% undera 30 lb. load. Strips from the same felt, but treated according to myprocess, when subjected to the same hydrosulphite solution for the samelength of time showed, aftertreatment, a strength of 63% lbs. and astretch of only 15% under a load of 30 lbs. Here, the strips treatedbymy process were appreciably stronger than the untreated strips but, whatis more important, thetest shows that my treatment prevents excessivestretching of the felt under moderate loads.

As a protection against the injurious action of sulphurous acid solutionmy treatment is also helpful.

New felt strips having a normal wet breaking It should be pointed outthat my process is appreciable strength after being subjected for Y 3hours to the action of a 10 volume hydrogen peroxide solution at aboutF. while untreated strips retained a substantial portion of theirinitial strength after the same treatment.

, What I claim is:

1. The method of treating a mechanical fabric of the character describedformed in substantial part of wool fibers to enhance its resistance tostretching and disintegration caused by exposure to alkaline solutions,hydrosulphites, sulfur dioxide, chlorine and hypochlorous acid whichcomprises chroming the fabric by treating it with an acid solution of analkali dichromate and thereafter treating the fabric with a reducingagent .to reduce the chrome therein to chromiumoxide.v

2. The method set forth in claim 1 in which the operation is conductedat'a temperature of from about F. to F.

- 3. The method of treating a mechanical fabric to alkaline solutions,hydrosulphites; sulfur dioxide, chlorine and hypochlorous acid whichcomprises chroming the fabric by treating it with an acid solution of analkali dichromate until is ac--.

quires a dark brown color and thereafter treating the fabric with areducing agent to reduce the chrome therein to chromium oxide.

4. The method set forth in claim 1 in. which the fabric is washed withwater after chroming and before the reduction treatment.

5. The method of treating a mechanical fabric of the character describedformed in substantial part of wool fibers to enhance its resistance tostretching and disintegration caused by exposure to alkaline solutions,hydrosulphites, sulfur dioxide, chlorine, and hypochlorous acid whichcomprises chroming the fabric by treatingit in an acid solution of achromium compound selected from the group consisting of chromiumtrioxide and the chromates and dichromates of ammonium, potassium,sodium, lithium, calcium, strontium and barium, until it acquires a darkbrown color and thereafter treating the fabric with a reducing agent toreduce a substantial portion of the chrome therein to chromic oxide.

6. The method of treating a mechanical fabric of the character describedformed in substantial part of wool fibers to enhance its resistance tostretching and disintegration caused by exposure to alkaline solutions,hydrosulphites, sulfur dioxide, chlorine, and hypochlorous acid whichcomprises chroming the fabric by treating it in an acid solution of achromium compound selected from the group consisting of chromiumtrioxide and the chromates and dichromates of ammonium, potassium}sodium, lithium, calcium, strontium and barium, until it acquires a darkbrown color and thereafter treating the fabric in an acid solution ofsodium thiosulphate to reduce a substantial-portion of the chrometherein to chromium oxide.

' CARLTON C. GORDON.

